Telephone system



Dec. 30, 1941. R. E. HERSEY TELEPHONE SYSTEM Filed June 12, 1940 11Sheets-Sheet l /A/ VEA/TOR R. E. HERSE V A TTORN-V Dec. 30, 1941. R. E.HERsEY TELEPHONE SYSTEM Filed June l2,- 1940 ll Sheets-Sheet 2 ATTOR/VEV 11 Sheets-Sheet 3 R. E. HERSEY TELEPHONE SYSTEM Filed June 12,1940 J vb@ h IWF. hl TIIH NR 3% @E Dec. 30, 1941.

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TELEPHONE SYSTEM Dec. 30, 1941.

Filed June l2, 1940 1l Sheets-Sheet 4 /NVENTOR Rf. HERSEY WW1/WKATTORNEY Dec. 30, 1941.

R. E. HERsEY l TELEPHONE SYSTEM Filed June 12,y 1940 11 sheets-,sheet 5.w MM m5% WHW. EHW.. Rim y, B

Dec. 30, 1941. R. E. HERsEY 2,268,397 -Y TELEPHONE SYSTEM Filed June 12,1940 1l Sheets-Sheet 6 /NVEA/TOR R E. HERSEY Dec. 3o, 1941.

R. E. HERsEY TELEPHONE SYSTEM Filed June 12, 1940 11 Sheets-Sheet 7/Nl/E/V TOR R. E. HERSEV WV? WWW ATTORNEY Deso, 1941. REHERSEY lv2,268,397'

TELEPHONE SYSTEM A TIGR/VFY Dec. 30, 1941.

R. E. H ERSEY TELEPHOM: SYSTEM Filed June l2, 1940 1l SheetS-Sheekl 9 yEFLILHI'Q,

NVEA/TOR R. E. HERSEV WW WW Dcc. 30, 1941. R. E. Hl-:RsEY

TELEPHONE SYSTEM Filed June 12, 1940 1l Sheets-Sheet 10 /NVE N TOR 'e EHERSEV R. E. HERSEY TELEPHONE SYSTEM Filed June 12, 1940 1llSheets-Sheat 11 UWE/v70@ By R. E. HERSEV Patented Dec. 30, 1941 UNITEDSTATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation 'of New York Application June 12, 1940,Serial No. 340,073

20 Claims.

This invention relates to telephone systems and particularly to those inwhich automatic switching mechanism is used for establishingconnections.

The objects of the invention are to improve the facilities forintercepting calls made to a particular subscribers line during hisabsence; to direct these calls automatically to a predetermined station,such as an operators position, without requiring any special effort onthe part of the calling subscribers; and to make other improvements insystems 'of this character.

In one form of the system whereby the foregoing objects of the inventionare realized one of the service operators in the central oiiice, havingbeen called in the usual manner by a subscriber entitled to this specialservice and notified that he expects to be absent from his telephone,establishes a connection from her position over a special trunk circuitthrough the automatic switches to the subscribers line. To. establishthis connection the operator transmits the impulses representing thesubscribers designation, and the designation is registered in a registersender and also in a designation register associated with the specialtrunk used bythe operator. The register sender cooperates with aswitch-controlling marker to operate incoming and nal selector switches,which may be of the cross-bar type, to complete the connection over 30the special trunk to the subscribers line. In an alternative form of thesystem the subscriber unassisted by the operator sets up a connectionover another special service trunk between the operators position andhis own line. In either case the connection thus established ismaintained during the subscribers absence, the subscribers numberremains registered on the designation register, and a busy condition isimpressed upon the subscribers line. Thereafter when the marker attemptsto complete a call to a busy line, the designation of the busy calledline registered in the marker is compared with the'designation of theabsent subscribers line, which is registered in the designationregister. Hence when the absent subscriber is called, the comparedregistrations match; whereupon the marker, being notied thereof, cancelsthe registration it has received pertaining to the called line andextends the calling line automatically to the particular special trunkused for intercepting the calls to said absent subscribers line. Thecalling party is now in telephonie connection with the operator, and shetakes any message he wishes to leave and communicates it to the absentsubscriber upon his return.

A feature of the invention, therefore, is a system in which the numberof a subscribers line is registered during his absence and his line madebusy; in which the numbers of all lines called thereafter and found busyare compared with the registered number; and in which any calling lineis automatically routed to an operator as a result of the match thatoccurs when the calling subscriber attempts to call said absentsubscribers line.

Another feature is a special intercept trunk which the operator uses toset up a conversational connection over the automatic switches to anabsent subscribers line, and which also has an appearance'as a calledcircuit in said switches and is seized automatically to establish aconversational connection between a calling line and the operatorwhenever the calling subscriber attempts to call said absent subscribersline.

Another feature is a special trunk which the subscriber, who expects tobe absent from his telephone, uses to set up a connection over theautomatic switches between the operators position and his own line, andwhich also has an appearance as a called circuit in said switches and isseized automatically to establish a connection between a calling lineand the operator Whenever the calling subscriber attempts to call theabsent subscribers line.

Another feature of the invention is an arrangementin which ringingcurrent is automatically applied to the absent subscribers line by wayof the special trunk connection when a calling line is extended as aboveexplained to the special trunk following the unsuccessful attempt tocomplete the desired connection to the absent subscribers line.

vA further feature of the invention is an arrangement in which theoperator sends a momentary signal over the special trunk circuit to tripthe ringing operation and thereby discontinue the application of ringingcurrent to the absent Vsubscribers line. By arranging the system so thatringing current is always applied to the absent subscribers linewhenever a call is intercepted the subscriber is given an opportunity'to answer the call in case he returns to his telephone while theintercepting facilities are still in operation. On the other hand someprovision must be made for tripping the ringing operation so that theoperator may converse with the calling party in the event the calledsubscriber has not returned to his telephone. This is accomplished, asabove noted by a special signal transmitted from the operators position.

The foregoing and other features of the invention will be described morefully in the following detailed speciication.

In the drawings accompanying this specification:

Figs. 1 and 2 constitute a general diagram of the system in which theinvention is incorporated; Figs. 3 to 11, inclusive, disclose thedetails of the system; and Fig. 12 is a diagram showing the relativelocations of Figs. 3 to 11.

Fig. 3 illustrates the service Operators position and shows the outgoingend of one of the special intercept trunks;

Fig. 4 shows the incoming end ofthe intercept trunk circuit;

Fig. 5 illustrates the incoming selector switch in which the intercepttrunk terminates and a nal selector switch for extending the trunkthrough to the subscribers line entitled to the special service. Thisfigure also illustrates the incoming and iinal selector switches forextending a calling line through to the special service trunk.

Fig. 6 shows a register individual to the intercept trunk forregistering the telephone number of the absent subscriber. This figurealso shows a connector for connecting the intercept trunk and thedesignation register to a register sender.

Fig. 7 illustrates the register sender;

Fig. 3 illustrates a switch-controlling marker and a marker connectorby. means of which the sender is connected to an idle marker;

Fig. 9 shows a number comparing circuit for comparing numbers registeredin the marker and the number of the absent subscriber; and

Figs. 10 and 11 show one of the special trunks by means of which thesubscriber may set up a connection between the operator and his ownline.

Although the invention is not so limited, it has been embodied for thepurpose of the present disclosure in a system using switches of thecrossbar type for establishing connections and register senders andmarkers for controlling the operation of these switches. Since theinventionis not particularly concerned with all of the detailed circuitsand apparatus employed in systems of this type, many of theseunessential details have been omitted in the present disclosure. For afull understanding of the operation of these systems reference may behad to Carpenter Patent 2,093,117 of September i4, 1937; CarpenterPatent 2,089,921 of August 10, 1937; Carpenter Patent 2,235,803 of March18, 1941; and the application by R. E. Hersey, Serial No. 300,928, ledOctober 24", 1939.

A general understanding oi the system may be had from the diagram shownin Figs. 1 and 2. These ngures disclose the incoming frames |00 and nalframes |0| of cross-bar switches comprising part of the terminatingequipment of a local cross-bar cnice. The regular traflic through theseframes to the called subscribers line is routed over incoming trunkcircuits from the local originating unit and from the originating unitsin the distant oihces. One of these incoming trunks, trunk |02, isillustrated. Incoming register senders, such as the sender |03, areassociated with the calling incoming trunk by means of the sender linkcircuits |04 and receive the designations of the called subscriberslines.

marker connectors |05 to idle switch-controlling markers, such as themarker |06. The marker receives the designation of the called line fromthe sender and connects itself to a number frame |01 for the purpose oftesting the called subscribers line and for determining the location ofthe line in the iinal switch frames Having determined the location ofthe incoming trunk and the called line, the marker is connected to theproper incoming and final frames through frame connectors |03 and |09.Following this, the links interconnecting the switches in the frames aretested, an idle path through these frames is selected, and the magnetsof the switches are operated to complete the 'desired coni nection.

The drawings also illustrate a special service or intercept operatorsposition IIB. This operators position may be in the same oiiicecontaining the terminating equipment, or it may be in a distant oilice.`In either case special service trunks ||I and 2 extend from theoperators position to the selectors on the incoming frame |00. Thesetrunks are provided with relays and controlling equipments ||3 and ||4at the incoming end, and each trunk also has an appearance, like asubscribers line, in the iinal switches on the frame |0|. The finalswitch appearance of trunk is represented by the line I5, and the finalswitch appearance of the trunk ||2 is represented by line IIG. specialservice'trunks is also provided with an individual designationregisterwhichserves to maintain a registration of the number of a. subscribersline`to which the special trunk isextended for intercept service. Forexample, the register ||1 is provided for the trunk andy a. similarregister I I8 is provided for the trunk ||2. The trunk is selected bythe operator for establishing an intercept connection to the line of asubscriber who has called her and requested the absentee service. Theother trunk |I2 is under control of the subscriber and may be selectedby him under control of his dial to set up the desired interceptconnection between the operator and his line.

A special incoming register sender H9 is provided for registering thedesignation required for extending a connection over one of thesespecial trunks to a subscribers line. Sender connectors |20 and |2| areprovided for connecting the special sender ||9 to the intercept trunksand to their associated designation registers. The sender ||9 also hasaccess through the marker connectors |05 to the commonswitch-controlling markers. A designation comparer |28, which is commonto the markers, is connectable to any marker and is also associated withthe designation registers I and I8 for the purpose of comparing thenumbers of lines that are called and found busy with the numbers thatare registered on the designation registers |I`| and IIB.

The district and office frames |22 and |23 of the originating office,located in the same oillce with the frames |00 and IUI of theterminating unit, are also illustrated. Calling subscribers lines in theoice are extended through the switches on the frame |0I, which serve asline switches as well as final switches, over district junctors, suchlas the junctor |26, to the district frame |22. 'I'he oilice frame hasaccess to outgoing trunks to the same and other offices, to

These senders are connected through L".

special service trunks, such as trunk I2, and also to operators trunks,such as the trunk |24, to the Each of the service operators positionwhich may be in the same or another oiiice.

Assume that the subscriber of line |25 wishes to have calls to his lineintercepted during his absence. Before leaving his telephone he may callthe special service operator in the usual manner by dialing the propercode to set the originating sender |32 and marker |33, which control thedistrict and oii'ice switches |22 and |23 to extend his line over thedistrict junctor |26 and over trunk |24 to the operators position. Theoperator responds, and the subscriber advises her that he is about toleave his home or oce and Wishes to have all calls to his lineintercepted during his absence. 'Thereupon the operator seizes an idleone of the special service trunks, such as the trunk HI. Her act ofseizing this trunk causes the connector |20 to operate and connect thesender H9 to the trunk ||I through the control mechanism H3 and also toconnect the sender I I 9 to the designation register HI which isindividual to the trunk II I. When the operator receives the dial tone,she manipulates her dial |2'I to transmit over the trunk ||I a series ofimpulses representing the number of the subscribers line |25. Theseimpulses are registered in the sender I 9 in the usual manner, and atthe same time they are registered in the designation register I I'I. Thesender H9 seizes an idle marker |06 through the connector |05, and themarker proceeds to control the operation of the incoming and nalswitches to extend the intercept trunk IH through to the absentsubscribers line |25. Thereupon the marker |06, the sender H9 and theconnector |20 are released. However, the established connections betweenthe operators position and the subscribers line |25 and the registrationin the designation register II'I are maintained during the subscribersabsence, and the subscribers line |25 appears busy whenever a markermakes a test thereof during the time the special trunk connection ismaintained.

If on the other hand the subscriber wishes to set up the interceptconnection himself, he dials a code identifying the group includingtrunk H2 and also the number of his own line. The sender |32 and marker|33 control the district and office switches |22 and |23 to seize trunkH2, following which the number of the subscribers line is transferredfrom sender |32 to the incoming sender H9. The marker |06 then controlsthe incoming and final switches |00 and |0| to exi tend the trunk H2 tothe subscribers line |25, omitting the busy test. At the same time theoperator is signalled over trunk H2. She informs the subscriber theconnection has been set up, and he then hangs up his receiver. Thereplacement of his receiver releases the connection from his line |25through switches IOI, |22 and |23 to the trunk H2, leaving theestablished connection between the operator and line |25 by way of thespecial trunk H2.

Each time during the subscribers absence that the marker |06 or any ofthe other markers attempts to set up a connection to another called lineand nds it busy, it operates the connector |29 to associate itself withthe comparing device |28. The device |28 then proceeds to compare thenumber of the busy called line, which is still registered in the marker|05, with the number of the absent subscribers line, which is registeredon the designation register H1 or H8 as the case may be and also withal1 other absent subscribers numbers which may be registered in otherdesignation registers. The purpose of this comparison is to determinewhether the busy called line is the line of an absent subscriber who hasrequested the intercept service. If, therefore, the subscriber of acalling line |30 attempts to call the absent subscribers line |25, thecomparison shows that the number in the marker |06 is the s arne as thenumber registered in the register H'I, and the marker is notified ofthis fact. The marker then proceeds to operate the incoming and iinalswitches to automatically route the calling incoming trunk |02 throughthese switches over the circuit H5 to the special intercept trunk whichwas used by the 0perator to set up the intercept connection to the line|25. When this connection is established from the calling line to theintercept trunk I, a signal is given the operator, and she responds andconverses with the calling subscriber. When the calling subscriber isthrough conversing with the operator, his connection is released, butther connection between the operator and the absent subscribers lineremains established.

Referring now to Figs. 3 to 9, the -outgoing end of one of the intercepttrunks 300 is shown terminating at the special service operatorsposition in the contacts of a key 30|, by means of which the operatorcan associate her telephone and position dial with the trunk and canalso hold the trunk while engaged on other calls. The trunk 300 is onethat is used by the operator in setting up an intercept connection andco-rresponds to the trunk H in Figs. 1 and 2. The incoming end of thetrunk 300 appears in the contacts 500 of an incoming selector switch 5Hand also appears in the contacts of the senderconnector relay 600. Theincoming end of the intercept trunk is also connected to a set ofcontacts 50| in one of the switches 5I8 on the final frame. -Moreoventhe incoming trunk circuit is provided with a number of relays forapplying ringing current, for controlling supervision, and for trippingthe ringing operation either under control of the called subscriber orunder the control of the service operator.

The register sender shown in Fig. 7 includes the usual controlling andimpulse receiving relays and register means for registering the digitsof a subscribers designation received in the form of impulse series.'I'he register comprises a crossbar switch having Vertical rows ofcontacts for the usual thousands, hundreds, tens and units digits andfor the incoming frame identiiication. Although some of the controllingrelays and circuits are shown in detail, many of the relays and circuitsthat would ordinarily be included in the sender have been omitted andare illustrated in a general way by the rectangle '100.

The designation register shown in Fig. 6 also consists of a cross-barswitch having' four vertical rows of contacts, one for each of the fournumerals of the subscribers designation. This register, which isindividual to the incoming trunk shown in Fig. 4, is connected to thesender by the connector relay 600 at the same time the incoming trunk isassociated with the sender.

The switch-controlling marker 800 includes registers 802, S03 and 804for registering the thousands, hundreds, tens and units digits,respectively, of the subscribers number which it receives from thesender by way of the marker connector 805. The marker also contains aframe indication register 806 on which it records the frameidentification of the trunk circuit 30,0,

The designation comparing circuit, which .is shown in Fig. 9, comprisesfour registers S00, 90|, 002 and 903 for the thousands, hundreds, tensand units digits of Va Subscribers number. This circuit also includes agroup of four relays 904 for each one of the special intercept trunksappearing in the incoming frame. The windings of the relays of theregisters 800,v 90|, 902 and 903 extend through the connector 801 to themarker, and the registers 80|, 802, 803 and 804 in the marker serve tooperate these relays to duplicate in the comparing circuit the numberregistered in the marker. The contacts of the register relays in thecomparing circuit are wired to the contacts of each of the cross-bardesignation registers. Therefore, whenever the number registered in themarker is found to be the same as the number on the designation registerassociated with a particular intercept trunk, all four of the relays ofthe group 904 individual to that intercept trunk are operated. Therelays of the group 904 when operated serve, as will be explainedhereinafter, to notify the marker that the absent subscribers line hasbeen called.

The operation of the system will now be described in detail. Assume forthis purpose that the subscriber of line 502 is about to leave hisresidence or oflice and wishes to have all calls to his line interceptedby the operator. Having called and notied the operator of hisintentions, the calling subscriber may leave immediately or he may waitto satisfy himself that the operator has successfully established theintercept connection to his line. In any event the operator proceeds toset up the connection by operating the two-way key from its normalposition to the position for closing the contact springs 302, 303 and304. The closure of these contacts associates the operators dial 305with the trunk 300, and a circuit is closed from battery through theupper left Winding of repeating coil 306, closed Contact spring 302Ythrough ini-` pulse contacts of the dial 305 thence through the closedspring contacts 303 and the lower left winding of coil 306 and windingof impulse relay 301 to ground. Relay 301 operates and closes apreliminary energizing circuit for relay 400 at distant end of thetrunk. At the same time a e circuit is closed from battery through thewinding of relay 308, contacts 304 and the normally closed contacts 309.associated with the dial 305. Relay 308 operates and disconnects thetrunk conductors 3|0 and 3|| from the bridge through the contacts ofrelay 301 and connects these conductors through the right windings ofthe repeating coil 306 and the polarized supervisory relay 3|2. Acircuit for relay 400 may now be traced from battery through the upperwinding of relay 400, normal contacts of relay 40|, conductor 3|0,contacts of relay 308 through the repeating coil windings and polarizedrelay 3|2 through the lower contacts of relay 308, conductor 3| normalcontacts of relay 40| to ground through the lowe': winding of relay 400.Relay 400 remains operated in this circuit; and the direction of thecurrent iiow over the trunk is such that polarized relay 3|2 does notoperate.

Relay 400 closes a circuit from ground through its armature and frontcontact, normal contacts of slow-release relay 402 through the windingof slow-release relay 403 to battery. Relay 403 operates and closes acircuit from ground through its contacts over the start conductor 404through 75' the winding of preference relay to battery; Relay operatesand opens the battery Supply for any other preference relay that mayhave operated at this time` A circuit is now closed from ground throughthe back contacts of, prei.'- erence relays 602 and 603. front Contactof relay 60| t0 ground through the winding of relay- 600. Relay 600operates and extends aJ number' of leads from the trunk. 300 through tothe register sender and also extends the. operating conduce tors for theselect and hold magnets of; the, desig? nation. register S04 through tothe resister sender. The operation of relay 600 closes a holding circuitfor relay 60| traceable from battery through the winding of relay 60|,@Ontacts ci relay 600, Conductor 605 to ground at the. back Contact ofthe sender release relay 10|., Relay 600 also closes circuits for thescndcrot-normal relay 102 and relay 105. The circuit f0.1. relay 102 istraceable from battery through lthe wind* ing of said relay, normalcontacts of relay 103, conductor 104 through contacts of the relay 000to ground. The circuit for relay 105 may be traced from battery throughthe winding of said relay, conductor 106, normal contacts of the holdmagnet 101, conductor 108 to ground through the contacts of relay 600.Relay 103 also operates in a circuit from battery through its wind--`ing, frcnt contacts of relay 102 to the grounded conductor 605.. Relay102 is now held energized in a circuit from battery through its Windingand front contacts to the grounded conductor 605.

The identity of the incoming frame in which the trunk 300 appears is nowregistered on the fourth vertical row of contacts in the register switch109 of the sender. To this end the relay 105 in operating extends theoperating circuits for the ten select magnets 1|0, 1||, 1|2, etc.,through the connector 600 to the terminal block 405 associated with thetrunk v300. Assuming that the terminal associated with conductor 406 isgrounded, a circuit is completed over this conductor through thecontacts of relay 600, conductor 028, contacts of relay 105, conductcr1|3 through the winding of select magnet 1|4 to battery. Magnet 1|4operates and prepares the contacts in the horizontal row associatedthereF with. Following the operation of magnet 1|4 a circuit is closedover the conductor 1|5 and through the winding of the hold magnet 101 tobattery. Magnet 101 operates and closes the cross-point contacts toregister the frame identication. Magnet 101 locks in a circuit frombattery through its winding and contact, conductor 1I0 to ground at thefront contacts of relay 102. Magnet 101 in operating opens the circuitof relay 105, and this relay releases, opening in turn the circuit ofthe select magnet `1|4. The magnet 1|4 releases, and the crossfpointcontacts are held closed by the continued ener, gization of the holdmagnet 101.

When relay 105 releases following the registration of the frameidentification, a circuit is closed for operating relay 40| in thetrunk, circuit may be traced from battery through the Winding of relay40|, conductor 4 01, contacts of relay 600, conductor 606, contacts o frelay 1|1, closed contacts of relay 103 to ground at the back contactsof relay 105. Relay 40| disconnects the windings of relay 400 from thetrunk 300, and relay 400 releases. Relay 400 opens the original circuitof relay 403, but this relay is now held in a circuit from batterythrough its winding and contacts to ground at the contacts of relay 40|.Meanwhilethe pulsing circuit has been completed from the trunk 300 tothe impulse relay 1|8 in the sender. 'Ihis circuit may be traced frombattery through the winding of relay 1|8, front contacts of relay 102,back contacts of relay 1|1, conductor 1| 9, contacts of relay 600,conductor 601 to the tip conductor 3|0 of the trunk and thence aspreviously traced through the repeating coil windings 306 and returningover the ring conductor 3| I, conductor 608, contacts of relay 000,conductor 609, contacts of relays 1|1 and 102 through the secondarywinding of the tone coil 120. The direction of current iiow over thetrunk is the same as before; consequently the polarized relay 3|2remains deenergized. At the proper time tone current is applied to thecoil 120, and the operator, hearing the tone in her receiver, proceedsto dial the number of the subscribers line 502.

Assuming the number of line 502 is 2345, the operator transmits with herdial 305 four corresponding series of impulses. As the dial moves awayfrom normal preparatory to the transmission of each series, theoil-normal contacts 309 open and relay 308 releases, closing the trunk300 through the contacts of the pulse relay 301. At each interruption ofthe circuit of relay 301 the relay releases and opens the circuit ofpulse relay 1|8. The pulse relay 'H8 operates the pulse and sequencemechanism 100, and at the end of each series of impulses a circuit isclosed for operating the proper one of the select magnets of theregister switch-109. Since the thousands digit is 2, ground potential isapplied to conductor 12| by the impulse circuit 100. Parallel circuitsmay now be traced for operating the No. 2` select magnet 122 of thesender register 109 and the No. 2 select magnet 6|0 of the designationregister 604. The circuit for magnet 122 eX- tends from battery throughthe winding of said magnet to the grounded conductor 12|; and thercircuit for magnet |0 extends from battery through its winding overconductor 6|| through contacts of relay 600 thence over conductor 14| tothe grounded conductor 12|'.l Thereupon ground potential is applied toconductor 123 and parallel circuits are closed through the thousandshold magnet 124 of register 109 and the thousands hold magnet 6|2 ofregister 604. Magnet 124 locks through its own contact to the holdingconductor 125; and magnet 6| 2 locks through its own contact overconductor 6|3 to ground at the closed contacts of relay 403l Followingthe operation of hold magnets 124 and 6|2 the'select magnets 122 and 5|0are released, preparing the switches for registering the next digit. Inlike manner the hundreds, tens and units digits are received and causethe operation of select magnets 126, 121 and 128, respectively, ofswitch 109, and select magnets 6|4, SI5 and 6|6, respectively, of switchG04. The successive operations of these select magnets are followed bythe operations of the corresponding hold magnets 129, 130 and 13| ofswitch 109 and hold magnets 6|1, 6|8 and 6|9 of switch 604. The selectmagnets are released, and the hold magnets are held over obvious lockingcircuits.

As soon as the units digit is registered, a circuit is closed fromground through the front contact of the units hold magnet 13|, conductor132 through the winding of relay 1|1 to battery. This relay operates andcloses an operating circuit for slow release relay 402 in the trunk.This circuit may be traced from battery through the vwinding of relay402, conductor 408, contact of relay 000, conductor 620, closed contactsof relay 1I1. to ground at the front contacts of relay 103.v At the sametime relay 1|1 opens the pre- Viously traced circuit for relay 40|, andthe latter relay releases. Relay 400 is again connected to the trunk300, the direction of current flow over the trunk being the same asbefore. Hence the lpolarized supervisory relay 3|2 at the outgoing endof the trunk remains deenergized. Relay 1| 1 in the sender also opensthe impulse circuit, disconnecting the impulse relay 1|8 from the trunk300, Relay 402 in the trunk circuit is held in a locking circuit frombattery through its winding and front contact to ground at the frontcontact of relay 400. After an interval slow-release relay 403 releasesand opens the energizing circuit of preference relay 60|. Relay 60|,however, remains locked through the contacts of relay 600 until thesender releases. Relay 403 opensits grounded connection to the conductor6|3, but ground is maintained on this conductor by relay 402 to hold theselect magnets of the designation register 604.

Following the registration of the number in thel sender the startcircuit 133 is closed through the front contacts of magnet 13| thenceover conductor 134 to the start relay 823 of the marker connector 805,and the marker connector operates to connect the sender to an idlemarker 800. sender by the closure of the selected cross-points in thevertical rows of contacts of the cross-bar switch 109 is transferredover the groups of conductors 135, 136, 131 and 138 to the thousands,hundreds, tens and units registers 802, 803 and 804 in the marker.Similarly the registration of the frame identification is transferredvfrom the register sender over the group of conductors 139 to the frameregister 806 in the marker. The marker proceeds in the usual manner totest vthe called line 502 and to operate the switch magnets for closingthe incoming primary and secondary cross-points 500 and 503 and the nalprimary and secondary cross-points 504 and 505 to extend the trunkcircuit 300 through to the subscribers line 502. The hold magnets 506and 501 of the incoming switch and the hold magnets 508 and 509 of theiinal switch are held to maintain the connection in a circuit over thesleeve conductor 5|0 through the contacts of relay 409, conductor 4|| toground at the front contacts of relay 402.

During the operations of the marker a circuit Iis closed over conductor808 through the conf nector 805, conductor 809, contacts of relay 600,

conductor 62| to operate the relay 409 in the trunk circuit. Relay 409serves to extend a number of control conductors 4|0 through to themarker 800. Having successfully established the connection the markerproceeds to release, but before'doing so it closes a release circuit forthe sender traceable over conductor 322 through connector 805, conductor8|0 through the winding of relay 10| to battery. Relay 10| operates andcauses the release of the sender including the operated hold magnets ofthe register 109. Relay 10| also removes ground potential from conductor605, and relays 600 and 60| release, disconnecting the sender from thetrunk. The register 604, however, remains in its operated condition, thehold magnets being held by the grounded conductor 6 3.

While the trunk 300 is connected to the marker by way of conductors 4|0,the proper control relays in the trunk are operated to control theThereupon the number registered in the application of ringing current tothe called line. Assume, for example, that it is desired to applyringing current to the tip conductor of the sb-y scribers line 502. Thisbeing the case, the marker causesl the operation of relay 412 over acircuit from battery through the winding of said relay, contacts ofrelay 409, the latter relay be ing operated while the trunk is connectedto the marker, thence over conductor 413 to ground in the marker. Relay412 operates and locks in a circuit from battery through its winding andfront Contact, back contact of the .tripping relay 414, conductor 415 toground at the front contact of relay 402. At the same time the markercloses a circuit from ground over conductor 416 through the contacts ofrelay 409 and the wind; ing 411 to battery. Relay 41'1 also operates andlocks through its winding and contact and the back contact of relay 414to the grounded conducto'r 415. When thereafter the marker, havingcompleted the connection through to' the called line 502 as abovedescribed, releases the relay 409 and disconnects itself from the trunk,ringing current is applied through the incoming and final selectors 511and 512 to the line 502. The ringing circuit may be traced from thesource 418, front contact of relay 411-, winding of the tripping relay414, normal contact of relay 419, front contacts of relay 412, frontcontacts of relay 411, normal contacts of relays 409 and 420, tipconductor 521 thence through the switches 511 and 512 over the loop ofthe line 502 and returning through the switches to the ring conductor422, normal contacts of relays 420 and 409, front contacts of relays41'1 and 412 to ground.

If the subscriber of line 502 is waiting to verify the establishment ofthe intercepted connection before he leaves his telephone, he nowreplies by removing the receiver from the switch-hook. The closure ofthe subscribers loop operates the ringing trip relay 414 in thewell-known manner, and this relay causes the release of relays 412 and41'1. Relay 41'1 disconnects the ringing source and icloses the calledsubscribers line through to the windings of the supervisory relay 423.Relay 423 operates and closes a circuit from ground through its frontContact, front contacts of relay 402, conductor 434, resistance 442,through the winding of relay 401 and battery. Relay 401 operates andreverses the con-- nections of relay 400 to the tip and ring conductorsof trunk 300 extending toward the operators position. Relay 400 remainsenergized, and the reversal of current over the line causes relay 312 tooperate. In the meantime the operator, having completed the dialingoperation, throws the key 301 to the hold position, opening the contactsprings 302 and 303 and closing springs 313 and 314. Relay 308 is nowheld in a circuit closed to ground at thespring 314. When, therefore,the called subscriber answers and current is reversed to release therelay 312 as described, the signal lamp 315 is lighted in a circuitclosed from battery through the lamputo ground at the closed contact ofrelay 312 The operator, seeing the light 315knows that the subscriberhas answered. She then throws the key 301 back to the talking position,closing springs 302 and 303 and connecting her telephone set to thetrunk. She then speaks to the subscriber and notifies him that theintercept condition has been established for receiving calls to his lineduring his absence. Thereupon the subscriber replaces his receiver andleaves his CIM release of relay 400.-

telephone. Replacement of the receiver opens the loop and causes thereleasev of relay 423. Relay' 423 releases relay 401, and thecurrentflo'vl7 over the trunk is restored to its former directicri.lRelay 312 again releases and opens the circuit for l-ighting the lamp315. The key isinow restored to the holding position where it is leftuntil a call to the absent subscribers line is intercepted.

Should the subscriber of line 502 leave 'his telephone immediatelywithout waiting for the op erator to s'et up the intercept connection,it then becomes necessary for the operator to discon', tinue the ringingof his line. If, therefore, he does not answer his bell, the operatormomentarily throws the key 301 to the neutral position and then returnsit to the hold position. Inthe neutral position of the key both relay301 and 308 release; therefore, thel circuit of relay 400 is opened.Relay 400 releases and closes a circuit f'rom ground through its backcontact, winding of relay 424 to battery at the frontl contact of relay402. Relay 424 operates and closes a new locking circuit forslow-release relay 402 to replace the holding circuit just opened by theThe new locking circuit may be traced from battery through the windingand front contact of relay 402, frontcontact of relay 424, back contactof relay 400 to ground at the back contact of relay 423. Relay 424, alsocloses an obvious operating circuit for slowrelease relay 4 25. Relay425 closes a bridge across the trunk circuit to trip the ringingoperation. This bridge may be traced from the tip conductor 421,conductor 426, resistance 421, contacts of relay 425, conductor 428 tothe ring conducter 422. This bridge causes the operation of the trippingrelay 414, and relays 412 and 411 are released to discontinue theringing operation as above described. In the meanwhile, the operator hasrestoredthe key 301 to the hold position and relay 308 reoperates toclose the trunk circuit through the winding of relay 312. Relay 400thereupon reoperates, reclosing the hold circuit of relay 40 2 andopening the circuit of relay 424.. Relay 4 24 releases and in turncauses the release of relay 4725. I

During the subscribers absence the numbers of all lines that' are calledand found busy are compared with the registered number of the absentsubscriber in order that all calls intended for his line may beintercepted and extended to the lservice operator. The comparison ismade by the comparing mechanism shown in 9 which is common to themarkers. ach time a marker, such as the marker 800, receives andregisters the number of a called line and finds the line busy on makinga test thereof, it seizes the comparing mechanism and connects itselfthereto through the connector 0011. Thereupon the number of the busycalled line is transferred from the marker to the registers 900, 901,902 and 903 of the comparing mechanism. The comparing mechanism thendetermines whether the number it has received from the marker is thesame as the number registered on the designation register 604 pertainingto the absent subscribers line. If the compared numbers are notidentical, the usual busy tone isreturned to the calling subscriber;however, 'if they are identical, the marker proceeds to extend thecalling line to the operators position. When, therefore, a calling lineis extended to an incoming trunk circuit 515 on a call intended for theabsent subscribers line 502, the number 2345 is registered on theregisters 001, 802, 803 and 804 in the marker. The marker, having testedthe sleeve conductor |3 of the line, appearing in the number frame 5|4and having found the line busy, seizes the comparing mechanism andapplies ground potential over conductor 8|| through the connector 801,conductor 8|2, causing the operation of certain relays (not shown) inthe comparing circuit and resulting nally in the operation of relay 909.The thousands digit 2 is now transferred from the register 80| throughthe connector 801 and conductors 8|3 causing the operation of relay 906,the remaining relays 905, 901 and 908 remaining deenergized. In likemanner the hundreds, tens and units digits 345 are transferred overconductor groups 8|4, 8|5vand 8| 6 causing the operation of relays 9I0and 9|| of the hundreds register 90|, relay 9| 2 of the tens register902, and relay 9|3 of the units register 903, the other register relaysremaining deenergized.

Circuits are now extended through the contacts of the registers 900,90|, 902 and 903 to the corresponding rows of contacts in the crossbardesignation register 604 to determine whether the operated relays matchwith the operated cross-point contacts in the switch. The matchingcircuit for the thousands register may be traced from the groundedconductor 8I2, through the contacts of relay 909, conductor 9|4, backcontacts of relay 905, front contacts of relay 905, back contacts ofrelay 901, conductor 9| 5, through the cross-point contacts which wereclosed by the conjoint operation of select magnet 6I0 and hold magnetSI2 when the thousands digit 2 was registered, and which are maintainedclosed by the continued energization of the hold magnet 6I2, thence overconductor 622 through the winding of relay 9|6 to battery. The matchingcircuit for the hundreds digit may be traced from the grounded conductor9|4 through the front contacts of register relays 9|0 and 9|I, backcontacts of relay SI1, conductor 9|8 through the closed cross-pointcontacts in the vertical row controlled by the hold magnet 6|1 andreturning over conductor 623 through the winding of relay 9I9 tobattery. In like manner the matching circuits for the tens and unitsdigits are traceable from grounded conductor 9| 4 through t-he contactsof the tens register 902 to conductor 920 and through the contacts ofthe units register 903 to the `conductor 92|. Conductors 920 and 92| arefurther traceable through the closed cross-point contacts in the tensand units rows of the switch 604 and returning over conductors 624 andB25, respectively, through the windings of relays 922 and 923,respectively, to battery. Thus all of the relays of the group 904 areoperated indicating a match between the registered numbers. For a morecomplete disclosure and description of the number comparing circuit andits cooperative relation with the marker, reference is made to thecopending application by R. E. Hersey, Serial No. 300,928, led October24, 1939.

With all of the relays of the group 904 operated a circuit is closed asfollows for the relay 924: Battery through the winding of said relay,front contacts of relays 923, 922, 9|9 and 9I6 to ground. Relay 924locks in a circuit from battery through its winding and contact,conductor 925, ground at the back contact of relay 429. Relay 924 alsocloses an operating circuit for relay 429 traceable from battery throughthe winding of relay 429, conductor 430 to ground at the front contactof relay 924. Relay 429 operates and opens the temporary locking circuitcf relay 924, but the latter is held over its original operating circuitunder control of the marker. The marker 800 is now notified that theabsent subscribers line has been called and that the calling line shouldbe automatically routed to the service operators trunk 300. Thenotifying signal is sent to the marker by the relay 924, which operatedas a result of the matched designations. The signal circuit may betraced from ground through the front contacts of relay 924, conductor921 through connector 801, conductor 8I8 through the winding of a routerelay 8I1 in the marker. In the well-known manner the operation of theroute relay in the marker causes the marker to associate itself througha connector 8|9 and over a group of test conductors 820 with the numberframe 5|4 containing the group of intercept trunks extending from theservice operators position. Having connected itself to the number frame,the marker proceeds to test the group of intercept trunks in the samemanner that a marker ordinarily tests a private branch exchange group.Normally each one oi these intercept trunks appears busy at the numberframe 5I4. For example, the test conductor 5I5 of the intercept trunk300 is normally grounded at the back contact of relay 429, so that thetrunk will appear busy to a marker testing the group at the number frame5|4. Since, however, a call is about to be intercepted by this trunk,ground potential is removed from the test conductor 5|5 by relay 429which has just operated as above described. Therefore, when the markertests the group containing the intercept trunk 300, it will find thistrunk idle and all others busy. Consequently the marker selects thistrunk and also selects an idle set of links for extending the incomingtrunk 5I0, to which the calling line has already been extended, throughthe incoming and final switches 5I1 and 5|8 to the intercept trunk 300.Having tested the conductor 5|5 and found it idle, the marker 800applies ground potential over conductor 820 to conductor 5I5, resultingin the operation of relay 420 over a circuit traceable from batterythrough the winding of said relay, ront contacts of relay 429 to thegrounded conductor 5I5. Relay 420 closes a circuit for holding relay429, traceable from` battery through the winding and front contacts ofrelay 429 to ground at the front contact of relay 420. Relay 420 alsoextends the grounded conductor 5| 5 through its front contacts thenceover conductor 432 through the winding of the hold magnet 5I9 tobattery. Magnet 5I9 closes and holds the contacts 50| of the nalsecondary switch, and in the well-known manner, the marker also operatesthe hold magnets 520, 52| and 522 to close the iiaining cross-points inthe switches 5I1 and The marker releases, and the connection through theincoming and nal switches 5I1 and 5I8 is maintained by the hold magnets520, 52|, 522 and 5I9 which are h'eld in holding circuits extendingthrough the closed contacts of the switches to ground applied on theholding conductor 523 of the incoming trunk 5I5. Relay 420 is also heldin a circuit from battery through its winding and front contact,conductor 432 thence through the closed contacts of switches 5|8 and 5|1to the grounded conductor 523. Ringing current is also applied to th'esubscribers line 502 from the incoming trunk 5|6. The ringing circuitextends frorn the source 521, over the tip conductor 524, through thecontacts ci switches A511 and 518, conductor 525, through front'contracts of relay 420, 'thence over tip conductor 421, through theswitches 511 and 512 over the loop of the line 520, returning throughswitches 51'2 and 51 I, conductor 422, front contacts of relay 420,conductor 433 through the switches 518 and 511 to ring conductor 526.Since the called subscriber is absent and does not answer his telephone,it is necessary to signal the operator in order 'that she may trip theringing operation. At the time the calling line is being extended to theintercept trunk, a circuit is closed from ground through th'e frontcontacts of relay 420, conductor 434, through the winding of relay 401to battery. Relay 401 operates and reverses the connection of thewindings of relay 400 to the `trunk 300. This reversal causes theoperation of relay 312 at the originating end of the trunk, and thisrelay closes an obvious circuit for lighting the lamp 315. The operator,seeing the lamp lighted, throws the key 301 to the talking position andchallenges. Receiving no reply she knows that a call is beingintercepted and that she should trip the ringing operation. To do this|she throws the key momentarily to the midposition to open the trunkcircuit 300. Relay 400 releases and operates relay 424 as abovedescribed. Relay 424 holds relay 402 and operates slow-release relay425. Relay 425 closes a bridge for tripping Jthe ringing operation. Thetripping circuit may be traced from the ringing source in the incomingtrunk 516 thence over conductor contact of relay 435 to ground at th'econtacts of relay 420. After a moment the operator throws the key 301from the mid-position to the talking position, and relay 308 operates toreclose the trunk 300 through the winding of polarized relay 312.YThereupon relay 400 reoperates and releases relay 424. After aninterval relay re leases and a circuit is closed from ground to the backcontact of said relay, front contact of relay 435, winding of relay 43Bto battery. Relay 435 operates and completes the talking circuit betweenthe operators position and the calling subscribers line. Talking currentis supplied toward the originating end of the trunk 300 through thewindings of relay 400. Th'e talking circuit from the incoming end of thetrunk 300 toward the calling subscribers line may be traced from batterythrough the lower winding of relay 423, conductor 431, conductor 43B,front contacts of relay 435, conductor 428, front contacts of relay421i,

conductor 433 and thence through the switches extend through thewindings of a batterysupply relay similar to the relay 423 of theintercept trunk 300. The windings of the relay in trunk 515 may beconnected in either direction. 1f they are connected in the samedirection as the windings of relay 423, no current flows and neither therelay 423 nor the relay in the incoming trunk 516 will operate. Theoperator now |speaks to the calling subscriber, advises him that thecalled party is absent, and offers to take'any message that the callingsubscriber may Wish to leave for subsequent communication to the absentsubscriber.

After the operator and the calling subscriber have nni'shed theirconversation the'callingsubscriber replaces his receiver and releasesthe connection he has established from his line through' the switches511 and 518. The release of this connection removes ground potentialVfrom conductor 432, and relay 420 releases to open the tip and ringconductors of the trunk 300 which appear in the cross-point contacts 501of the final switch 518. Relay 420 in turn releases relay 429, whichrestores the normal busy potential-to 'th'e conductor 515 of theintercept trunk 300. 'Relay 420 also releases relays 435 and 401 andrelay 435 releases relay 436. Relay 401 reverses the direction of thecurrent over the 'trunk 300, and relay 312 releases. TheV operatorrestores' her key to the `hold position and notes that the lamp 315 isdark, indicating that the calling subscriber has replaced his receiver.The equipment is now in the same condition that existed prior tothe callto the absent subscribers line; `that is to say, the intercept trunk30'0 remains connected to the absent subscribers line through theswitches 51 1 and 512, and the absent subscribers number remainsregistered on ythe designation register 604 in readiness for interceptngthenext call made to the line 502;

Should the absent subscriber return while his bell is being rung on acall that is about to be intercepted he may answer inthe usual manner byremoving his receiver. The removal of .his receiver trips the ringingmechanism in the calling incoming trunk 516, the tripping circuit beingtraceable from conductor 524, through switches 511 and 518, .conductor525, front contacts of relay 420, conductor 421, lswitches 511 and 512,over the closed loop of the line 502 and returning through switches 512and 511, conductor 422, front contacts of relay 420, conductor 433through the switches 518 and 511 to'conductor 5215. The calledsubscriber may now speak to the calling party. In `the meantime the0perator, having observed the lighted lamp 315, throws the key 301 tothe intermediate position, causing the release Aof relay 400 and theoperation of relays 424, 425 and 435 as above described. Relay 43'5locks in a circuit from battery through the front contacts of relay 402,winding and front contacts of relay 435 to ground at the front contactof relay 420. When the operator subsequently moves thevk'ey to thetalking position, relay 400 reoperates, and relaysw424 and 425 releaseand relay 435 operatesv to extend the talking connection from the trunk300 to a called subscribers line 502. The operator now challenges anddiscovers that the absent -subscriber has returned to his telephone andhas `answered the calling party. While the trunk 300 is extended throughrelay 4311` to the established connection between the calling and calledparties, supervisory relay `423 is operated in a circuit inducing theloop of the called une 502, and the same is true of the correspondingsupervisory relay in the incoming trunk 5| 6. After learning that thecalled party has answered, the operator throws the key 30| to the holdposition and the energizing circuit of relay 400 is maintained, andrelay 402 is held by relay 400. As soon as the supervisory relay 423 isoperated, relay 40| is operated, and relay 3|2 is operated at theoriginating end of a trunk to light the supervisory lamp 3|0 as a signalto the operator that the called subscriber has his receiver oli theswitchhook. i When the calling subscriber replaces his receiver, theconnection to the called partys line 502 is released, and relays 420 and429 are deenergized. If the called subscriber 502 still has his receiveroiT the switchhook the circuit of relay 423 is reclosed and relay 435 isnow held in a circuit from battery through the front contact of relay402, winding and front contact of relay 435, conductor 434, frontContact of relay 402 to ground at the front contact of relay 423. Whenthe subscriber of line 502 iinally restores his receiver, relay 423releases, and relays 435 and 435 release. The release of relay 423 opensthe circuit of relay 40| and relay 3|2 releases to eX- tinguish the lamp3|5.

Should the absent subscriber return and wish to discontinue theintercept service, he may do so by merely removing his receiver from theswitchhook. The removal of the receiver closes the circuit of relay 423,and this relay in turn closes the circuit for relay 40|. Relay 40|reverses the current direction, and the lamp 3| 5 is lighted at theoperators position. The operator responds by throwing the key 30|immediately to the talking position. Relay 400 remains energized andholds the relay 402 operated, and the operator now speaks to thesubscriber over the intercept trunk connection. He informs her that hedoes not wish the service any longer, and she instructs him to hold hisreceiver E the switchhook for a moment, in order that she may releasethe connection. While the subscriber is holding his receiver oi theswitchhook and relay 423 is energized, she throws the key 30| to theintermediate position and leaves it there. Relay 400 immediatelyreleases, and after an interval the slow-release relay 402 releases,since relay 423 is now operated. Relay 402 removes ground potential fromconductor 4||, and the incoming and nal switches 5| l and 5|2 arerestored to normal. Relay 402 also removes ground potential fromconductor 6|3, allowing the hold magnets 6|2, SI1, 6|8 and 6|9 torelease and restore the designation register 604 to its normalcondition. The subscriber of line 502 now replaces his receiver on theswitchhook, and his line is available for incoming and outgoing calls asusual.

A description will now be given of the operations involved When thesubscriber establishes the intercept connection to his own line withoutthe assistance of the operator. In this case the special intercept trunk|000 shown in Figs. 10 and-11 is used; accordingly, these figures shouldbe substituted for Figs. 3 and 4 in the drawings.

When the subscriber of line 502 wishes to set up the interceptconnection, he removes his receiver, resulting in the automaticextension of his line through the line switches to a district junctor|00| terminating in the district frame |002. An originating sender isassociated with the subscribers line, and he dials a code designationrepresenting the group of intercept trunks, including the trunk |000,following which he dials the numerical designation of his own line. Theoriginating sender and marker control the operation of the district andoffice switches |002 and |003 to seize the idle intercept trunk i000. Acircuit is now closed from battery through the upper Winding of relay||00 thence over conductor |0| through the contacts of relay H02,conductor |03 through the oice and district selectors |003 and |002,thence through the supervisory relay (not shown) in the district junctorl 00| and returning through the district and oiiice switches |002 and|003, over conductor |004, contacts of relay |02, through the lowerwinding of relay H00 to ground. Relay |I00 closes a circuit from groundthrough its front contact, normal contact of relay |04 through thewinding of slow-release relay ||05 to battery. Relay H05 closes acircuit from ground over conductor ||06 and 404 to operate the relay 60|in the manner previously described for the purpose of connecting theintercept trunk |000 to the idle register sender of Fig. 7. Relay ||05also closes a circuit from ground over conductor |01 and thence over thesleeve conductor ||08 to guard the trunk |000 against seizure by otheroice selector switches |003.

As soon as the incoming sender yof Fig. 'l is associated with the trunk|000, the numerical designation is transferred in the well-known mannerfrom the originating sender to the incoming sender. If the transfer ofthe designation is made by the usual revertive impulse method the pulseand sequence circuit |00 of the incoming sender may be arranged totransmit these revertive impulses back over the established connectionto satisfy the registrations in the originating sender. As thesenumerical designations are received in the terminating sender they causethe operation of the cross-bar registers '|09 and 604 in the manneralready described. 'I'hus the number of the subscribers own line 502,which he has dialed into the originating sender, is registered in theterminating sender of Fig. 7 and also on the register mechanism 604individual to the special service trunk |000.

Since the connection being established is one that reverts to thecalling line, which is, therefore, in a busy condition, it is necessaryto apprise the sender and marker of this fact in order that the usualbusy test may be omitted. This class information is sent to the senderby means of a circuit traceable from ground through the back contact ofrelay H04, conductor H09 thence over conductor 62| through contacts ofthe relay 600, conductor 809 to the sender control circuit '|00 whereappropriate relays may be operated to record the information.

After the numerical designation has been registered in the sender and inthe register mechanism 604, an idle marker is associated with the senderin the manner described, and the numerical registration is transferredto the marker together with the necessary class information fornotifying the marker that the called line is one that should be seizedWithout regard to its busy condition and. that the usual ringingoperation may be omitted. The marker sets up the connection in a mannerpreviously described, causing the operation of switches 5|| and 5|2 toextend the intercept trunk |000 through to the subscribers line 502.When the sender reaches the stage at which relay 'H1 is operated, relayH02, which was previously operated in the

